Re: file list in a directory

["Nick Roberts" <nickroberts@adaos.worldonline.co.uk>]

Is there a working doucment on this on the Internet anywhere?

One idea that occurred to me as to how an implementation could supply this
sort of facility, without actually requiring a special package, would be to
provide a special syntax for the file name when opening or creating a text
file, where the relevant names or other data/parameters were output/input as
lines of text. For example:

with Ada.Text_IO; use Ada.Text_IO;
procedure List_Ada is
   Name: String(1..200);
   Last: Natural;
   Search: File_Type;
begin
   Open(Search,In_File,"dir:*.ads;*.adb//source/ada/");
   Get_Line(Search,Name,Last);
   Put_Line(Name(1..Last));
   Close(Search);
end;

Operations such as copying, linking, archiving/backup, and inquiry and
update of attributes could be provided in a similar way. This technique
makes use of the file I/O idiom to provide a ready iterator. In particular
it says when a single search begins and ends (at opening and closing), so
that the list can be 'frozen' (or the directory locked) during the search.
It could also help with debugging, and help facilitate ersatz functionality.

Obviously, a definition of a standard name syntax would be advantageous.
This would be a technique that could have the advantage of being largely
language-independent.

A copying example might be:

with Ada.Text_IO; use Ada.Text_IO;
procedure Copy_Safely is
   Name: String(1..200);
   Last: Natural;
   Search, Copier: File_Type;
begin
   Open(Search,In_File,"dir:*.ads;*.adb//source/ada/");
   Create(Copier,Out_File,"copy:|//source/ada");
   Get_Line(Search,Name,Last);
   Put_Line(Copier, Name(1..Last) & "|backup/" & Name(1..Last) );
   Close(Search);
   Close(Copier);
end;

When the Copier file is closed, the copy operations are performed,
preferably with all-or-nothing semantics (if something goes wrong, an
exception is raised).

NB: These examples don't have the checking they should.

--
Nick Roberts
http://www.AdaOS.org



"Robert A Duff" <bobduff@world.std.com> wrote in message
news:wccelvxqxrj.fsf@world.std.com...
> Pascal Obry <p.obry@wanadoo.fr> writes:
>
> > Ada can't do that. Some program just don't have access to a file system
> > (e.g. embedded programs).
>
> Not a very good excuse, I think.  Ada has Text_IO, after all.
>
> The ARG is working on a portable (standard) Directory_Operations
> package, but it won't happen quickly.
>
> - Bob